Continuous puffing apparatus

ABSTRACT

A continuous puffing apparatus for puffing bits of products such as ready-to-eat breakfast cereals, meat analogs, and the like. The apparatus includes means for passing a stream of such product bits therethrough, means for internally circulating a stream of heated particles of solid heat transfer material such as salt granules around a closed, internal path so that the two streams are mingled for only one portion of the total length of the closed, internal path of the heat transfer material, and means for heating the stream of heat transfer material particles as they traverse a second portion of the closed path of travel to maintain them at a substantially uniform predetermined temperature. Thus, the stream of product bits are substantially precluded from direct exposure to the means for heating the stream of heat transfer material particles. In this manner, the product bits are heated so that puffing can be effected essentially only during the period they are mingled with the particles of heat transfer material. The puffing apparatus may also include means for being operated at an elevated pressure in which event, the particles are heated within the apparatus to a temperature which will induce puffing when the bits are subsequently exposed to atmospheric pressure upon emerging from the apparatus.

United States Patent [1 1 Liepa 11 3,744,398 July 10, 1973 CONTINUOUS PUFFING APPARATUS [75] inventor: Alexander L. Liepa, Cincinnati, Ohio [73] Assignee: The Procter & Gamble Company, Cincinnati, Ohio [22] Filed: May 1, 1972 [2]] Appl. No.: 248,847

[52] US. Cl. 99/323.4, 99/81 [51] Int. Cl A23i 1/18 [58] Field of Search 99/323.4, 323.5, 99/3239, 323.11, 81, 323.7, 323.8; 259/3 [56] References Cited UNITED STATES PATENTS 972,854 10/1910. l-lamrick..... 99/323.l1 1,050,180 l/l9l3 Taylor 99/323.1l 2,606,489 8/1952 Morsette 99/323.1l 3,253,533 5/1966 Benson 99/3234 7/1969 Heiland 99/3234 Primary Examiner-Robert W. Jenkins Attorney-Richard C. Witte et al.

57 ABSTRACT A continuous puffing apparatus for puffing bits of products such as ready-to-eat breakfast cereals, meat analogs, and the like. The apparatus includes means for passing a stream of such product bits therethrough, means for internally circulating a stream of heated particles of solid, heat transfer material such as salt granules around a closed, internal path so that the two streams are mingled for only one portion of the total length of the closed, internal path of the heat transfer material, and means for heating the stream of heat transfer material particles as they traverse a second portion of the closed path of travel to maintain them at a substantially uniform predetermined temperature. Thus, the stream of product bits are substantially precluded from direct exposure to the means for heating the stream of heat transfermaterial particles. In this manner, the product bits are heated so that puffing can be effected essentially only during the period they are mingled with the particles of heat transfer material. The puffing apparatus may also include means for being operated at an elevated pressure in which event, the particles are heated within the apparatus to a temperature which will induce puffing when the bits are subsequently exposed to atmospheric pressure upon emerging from the apparatus.

19 Claims, Drawing Figures 23 so TIC-Z5 T5 n. 32 iii 7 6| Pmmzm 3.744.398

sum a nr 5 1 CONTINUOUS PUFFING APPARATUS BACKGROUND OF THE INVENTION A Puffed ready-to-eat cereals having a light, porous structure are commercially marketed on a broad scale. Puffing is essentially the conversion of a relatively dense material to an expanded, porous structure, which is commonly achieved by causing moisture trapped within the material to change very rapidly from the liquid state to the vapor state. Puffing is commonly achieved through either intensely heating the material at or near ambient atmospheric pressure, or by heating the material at an elevated pressure to a temperature which, upon the release of the pressure, will cause the moisture within the particles of material to flash to steam. Although puffing is normally associated with breakfast cereals, puffing of other materials such as bits of synthetic meat (alternatively referred to as meat analogs) has been found desirable and useful for such purposes as improving their rehydration properties. Improving the rehydration property of dried material has been found to be very beneficial, for instance, where dehydrated bits of synthetic meat are to be utilized in casserole dishes.

DESCRIPTION OF THE PRIOR ART A puffing apparatus which includes means for mingling bits of material to be puffed with a granular heat transfer material such as salt (sodium chloride), or sand, steel shot, or the like wherein puffing is achieved by intense heating at atmospheric pressure is disclosed in U.S. Pat. No. 3,253,533 issued to John O. Benson, May 31, 1966. This apparatus utilizes heating means to heat the outside surface of a revolving pan whereby granules of heat transfer material and product bits are heated while mingled. The pan is rotated about an inclined axis with its open end at a higher elevation than its closed end. The pan has a perforated helical member 12 which acts to forward product bits upwardly and out of the pan while simultaneously permitting the bulk of the granulated heat transfer material to tumble and sift through the perforations so that it remains between the turns of the helical member within the pan. However, it is disclosed in that patent that some granulated heat transfer material will exit from the pan with the product bits. Therefore, the apparatus disclosed by the patent includes external means for separating such granules from product bits, and means for reintroducing the granules of heat transfer material into the pan.

U.S. Pat. No. 3,456,576 issued to Wolfgang K. Heiland et al., July 22, I969 discloses an example of the type of puffing apparatus wherein the material is heated at an elevated pressure to a temperature that will effect puffing upon ejecting the material from the apparatus.

Examples of related prior art which includes co-axial concentric screw conveyors are disclosed in U.S. Pat. No. 564,231 issued to Reuben O. Stutsman, July 21, 1896 and U.S. Pat. No. 1,996,347 issued to Roy R. Reppert, April 2, 1935.

Although the cited prior art is representative of apparatus including some of the elements of the present invention, none of these approaches has solved all of the problems associated with providing an apparatus for continuously puffing product bits in the manner of nor to the degree of the present invention.

SUMMARY OF THE INVENTION The nature and substance of the present invention will be more readily appreciated after giving consideration to its major aims and purposes. The principal objects of the present invention are recited in the ensuing paragraphs in order to provide a better appreciation of its important aspects prior to describing the details of a preferred embodiment in later portions of this description.

A major object of the present invention is providing a continuous puffing apparatus for passing a stream of product bits therethrough in which apparatus product bits are heated to effect puffing but are substantially precluded from direct contact with the primary heat source or any surface directly heated by the primary heat source so that scorching, burning and the like of the bits are substantially obviated.

Another object of the invention is providing a continuous puffing apparatus as described in the next paragraph hereinabove comprising a stationary primary heat source.

Yet another object of the present invention is providing a continuous puffing apparatus as described in the next paragraph hereinabove which may include means for pressurizing the apparatus so that the product bits can be heated, while pressurized, to a temperature that will induce puffing upon exposure to ambient pressure, as when the product bits are ejected from the pressurized zone of the apparatus.

Still another object of the present invention is providing a continuous puffing apparatus as described in the three paragraphs hereinabove which apparatus further comprises means for establishing a bypass flow of granular heat transfer material external to the puffing apparatus whereby the granular heat transfer material can be cleaned and/or replenished during the operation of the apparatus.

These and other objects are achieved by providing a continuous puffing apparatus comprising a revolvingly mounted drum assembly having therein a product heating zone and a heat transfer medium heating zone, means for receiving product bits into the product heating zone, means for internally circulating a stream of solid heat transfer material heated to a predetermined temperature around a closed path comprisingthe two heating zones in series relation, means for mingling the product bits with the stream of heated solid particles of heat transfer medium within the product heating zone to enable puffing the product bits for a predetermined period of time, means inside the apparatus for separating the product bits from the particles after the predetermined time, and means for discharging the product bits from the apparatus, said apparatus further com- A prising primary heating means for heating the stream of heat transfer material tothe predetermined temperature as the stream traverses the heat transfer medium heating zone. The primary heating means may comprise stationary heating means external to the drum. And, the apparatus may further comprise, singly or in combination, the following: means for pressurizing the heating zone; and, means for establishing a bypass flow of a portion of the stream of particles of heat transfer material external to the chamber so that such bypassing portion can be cleaned and/or replenished during the operation of the puffing apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter regarded as forming the present invention, it is believed the invention will be better understood from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a fragmentary, side elevational, sectional view of a preferred embodiment of the present invention which includes two screw conveyors disposed in co-axial, concentric relation.

FIG. 2 is a fragmentary sectional view of the preferred embodiment apparatus of FIG. 1 taken along line 22 thereof.

FIG. 3 is a fragmentary sectional view of the apparatus of FIG. 1 taken along line 3-3 thereof.

FIG. 4 is a fragmentary schematic showing means for heating a circulating stream of solid particles of a heat transfer medium to maintain the stream at a predetermined temperature.

FIG. 5 is a fragmentary, side elevational, partially sectional view of an alternate embodiment of the present invention of a continuous puffing apparatus including means for being operated at elevated pressure, the means for being operated at elevated pressure including a batching valve for introducing discrete charges of product bits into the heating zone of the apparatus and a similar batching valve for removing discrete charges of heated product bits after they have traversed the product heating zone of the apparatus.

FIG. 6 is an enlarged scale, side elevational sectional view of a batching valve as shown in FIG. 5.

FIG. 7 is an enlarged scale sectional view of the batching valve shown in FIG. 6 taken along line 7-7 thereof.

FIG. 8 is a fragmentary, side elevational, partially sectional view of a pressurizable embodiment of the present invention of a continuous puffing apparatus which includes means for removing a portion of the stream of circulating heat transfer material from the apparatus while operating, and means for introducing heat transfer material into the apparatus while operating so that a portion of the stream of circulating heat transfer material can be passed through external equipment so that such portion can be cleaned and/or replenished while the puffing apparatus is operating.

FIG. 9 is a fragmentary sectional view of the apparatus shown in FIG. 8 taken along line 9--9 thereof.

FIG. 10 is a fragmentary side elevational view of an alternate infeed assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, the preferred embodiment of the present invention, continuous puffing apparatus is shown to comprise rotatable drum assembly 21 and stationary heater 22; drum assembly 21 comprising co-axial, concentric screw conveyors having opposite conveying senses, the inner screw conveyor being designated the centerless screw conveyor 34 and the other screw conveyor being designated the annular screw conveyor 35. FIG. 1 further shows, in conjunction with apparatus 20: a hopper 23 and chute 24 for storing and conducting respectively product bits 25 so that a stream of product bits 25 enter one end of drum assembly 21 which is designated infeed end 26; and, a container 27 for receiving the stream of product bits 25 from the opposite end of drum assembly 21 which opposite end is designated discharge end 28.

Briefly stated, when drum assembly 2], FIG. I, is being revolved in the proper direction relative to the pitch of the screw conveyors, a stream of product bits 25 passes from left to right through the center portion of drum assembly 21 which portion is designated the product heating zone 29 and, while so passing, the product bits 25 are mingled with a stream of granules 30 of a heat transfer material such as salt (sodium chloride), sand, steel shot, or the like being circulated about a closed path which is wholly contained within drum assembly 21. The closed path includes movement from left to right in the center portion of drum assembly 21 induced by the action of the centermost screw conveyor 34 and includes movement from right to left in an annular portion of the drum assembly which movement is induced by the action of annular screw conveyor 35 which annular portion is designated the heat transfer material heating zone 31. The granules 30 comprising the stream of circulating heat transfer material is maintained substantially at a predetermined temperature by being heated by heater 22 through the cylindrical drum wall 32 of drum assembly 21 as the granules pass through heat transfer material heating zone 31. By rotating the drum assembly 21 about its axis 41 at a constant angular velocity by means not shown in the figures in order to promote clarity, product bits 25 pass through drum assembly 21 at a constant, predetermined velocity whereby they are mingled with the stream of heated granules 30 for a predetermined time whereby the product bits are uniformly heated. The predetermined temperature, designated 33 for convenience, is great enough to cause intense heating of product bits 25 so that any moisture within the product bits is rapidly converted to steam whereby the product bits are puffed. However, predetermined temperature 33 is low enough to insure that the product bits are not charred or scorched during their period of residence within drum assembly 21.

Drum assembly 21 of the preferred embodiment continuous puffing apparatus 20, FIG. 1, comprises, in addition to screw conveyors 34 and 35, means 36 for separating product bits 25 from being mingled with granules 30 within centerless screw conveyor 34, means for transferring such separated granules 30 from centerless screw conveyor 34 to annular screw conveyor 35, and means 37 for forwarding granules 30 from the left end of annular screw conveyor 35 radially inwardly into the left end of centerless screw conveyor 34. Thus, drum assembly 21 includes: means for conveying product bits 25 from left to right by the action of centerless screw conveyor 34 when the drum assembly 21 is rotated inthe proper direction about axis'4l so that the product bits emerge from the discharge end 28 of the drum assembly 21; means for mingling product bits 25 with granules 30 while being conveyed rightwardly by centerless screw conveyor 34; and means for internally circulating granules 30 so that they can be substantially maintained at predetermined temperature 33 by controlling heater 22, which heater is stationary and is located outside of drum assembly 21.

Centerless screw conveyor 34, FIG. 1, comprises a tubular wall 38, a helical member 39 and may include a number of baffles or fins 40.

Tubular wall 38, FIG. 1, comprises an imperforate portion 45 extending from its left end an axial length designated 1, and a perforate or foraminous portion 47 extending the remainder of its total axial length. The holes or perforations, designated 48, in foraminous portion 47 are sized to permit the passage of granules 39 of heat transfer material but to substantially preclude the passage therethrough of product bits 25. Thus, when drum assembly 21 is disposed so that its axis 41 extends generally horizontally as indicated in FIG. 1, with foraminous portion 47 disposed at the right end, and the drum assembly 21 is rotated about axis 41, the foraminous portion 47 acts as means for separating product bits 25 from granules and as means for transferring such separated granules from centerless screw conveyor 34 into annular screw conveyor 35 by permitting the granules to pass radially outwardly through the holes of perforations 48.

The helical member 39 has an outside diameter substantially equal to the inside diameter of tubular wall 38 and has a length parallel to axis 41 of drum assembly 21 which is substantially equal to the length of tubular wall 38. Helical member 39 is secured within tubular wall 38 by being press fit, welded, or by other suitable means so that the helical member 39 and tubular wall 38 become rigidly associated with each other whereby they rotate as a unit.

Referring now to FIG. 2, the inside diameter of the helical member forms an axially extending void 42 having a circular cross section through the center of the centerless screw conveyor, hence the centermost screw conveyor being designated centerless screw conveyor 34.

A plurality of baffles or fins are secured to the inwardly facing surface of tubular wall 38 intermediate the flights of helical member 39 so that they project inwardly. The fins act to increase the mixing or mingling of product bits 25 with granules 30 as the mingled bits and granules are forwarded from left to right by the centerless screw conveyor 34, FIG. 1.

Annular screw conveyor 35 of drum assembly 21, FIGS. l3, comprises tubular drum wall 38, a second helical member 55, and cylindrical wall 32 which also functions as the outer wall of drum assembly 21.

The second helical member has an inside diameter which is substantially equal to the outside diameter of tubular wall 38, has an outside diameter substantially equal to the inside diameter of drum wall 32, and has a length substantially equal to the axial length of tubular wall 38. Annular screw conveyor 35 may be assembled by shrink fitting, welding, or otherwise securing second helical member 55 to the radially outwardly facing surface of tubular wall 38; and by securing the radially outwardly facing helical surface of the second helical member to the radially inwardly facing surface of drum wall 32. In this manner, when drum assembly 21 is rotated about its axis 41, both the centerless screw conveyor 34 and the annular screw conveyor 35 are rotated synchronously as a single unit. Second helical member 55 is of the opposite hand with respect to the pitch of the first helical member 39, so that rotation of drum assembly 21 causes the two screw conveyors to have opposite conveying senses. As depicted in FIG. 1, if the drum assembly 21 is rotated in the direction to convey material within the centerless screw conveyor from left to right, the conveying sense of the annular screw conveyor will be from right to left.

Referring now to FIG. 1 and 3, the means 37 for forwarding granules 30 radially inwardly from the left end of annular screw conveyor 35 to the left end of centerless screw conveyor 34 is accomplished by providing a number of buckets 56 which in the preferred embodiment spiral outwardly from the outwardly facing surface of tubular wall 38 to the inwardly facing surface of drum wall 32, and by providing a number of apertures 59 in tubular wall 38 so that when drum assembly 21 is rotated in direction 57 granular heat transfer material is scooped from the bottom of annular screw conveyor 35 and, upon continued rotation of the drum assembly in direction 57 about axis 41 the granular material thus scooped from the bottom of drum assembly 21 will be funneled through apertures 59 as indicated by arrow 58 into centerless screw conveyor 34. Although the preferred embodiment drum assembly 21, as shown in FIG. 3, has three buckets 56 circumferentially spaced at equal intervals within the annulus intermediate walls 32 and 38, this number of buckets is not believed to be critical to the present invention.

Drum assembly 21, FIG. 1, is completed by securing left bulkhead 60 to the left end of the two concentric screw conveyors and by securing right bulkhead 61 to the right end of the two concentric screw conveyors. Left bulkhead 60 has a centrally disposed infeed aperture 62 for admitting product bits 25 into drum assembly 21, and right bulkhead 61 has a centrally disposed discharge aperture 63 therein having a diameter approximately equal to the inside diameter of the right end of the foraminous portion 47 of tubular wall 38 which enables the action of centerless screw conveyor 34 to discharge product bits 25 from centerless screw conveyor 34, such discharge being after the product bits 25 have been separated from being mingled with granules 30 of heat transfer material within the centerless screw conveyor.

Heater 22 of the preferred embodiment puffing apparatus 20, FIG. 1, is controlled by a closed-loop temperature control system 64 shown schematically in FIG. 4 to maintain the circulating stream of particles 30 of heat transfer material approximately at predetermined temperature 33 for the purpose of puffing bits 25 as hereinbefore described. However, it is not believed that such a closed-loop temperature control system is essential to the present invention; rather, it is believed that adequate manual or other temperature control schemes for practicing the present invention are well known to persons skilled in the art so will not be further discussed herein in conjunction with the present invention.

The closed-loop temperature control system 64, FIG. 4, comprises temperature probe 65, controller 66, control valve 67, manual valves 68, 69, heater 22, cables 77, 78, and piping 79 as indicated.

Briefly stated, the temperature control system 64 controls the temperature of granules 30 by sensing their temperature with temperature probe 65 connected' via cable 77 to controller 66 and by opening and closing or otherwise modulating control valve 67 to control the flow of combustible gas therethrough whereby flames 52 can be modulated as needed to substantially maintain the temperature of granules 30 at predetermined temperature 33 as hereinbefore discussed. Valves 68 and 69 provide system safety and flexibility by enabling manual shut-down and control of the system respectively.

A representative puffing apparatus, FIG. 1, constructed in accordance with the foregoing description of a preferred embodiment of the present invention has a production rate of one hundred pounds of puffed product bits per hour when rotated at about eight and thirty-five hundredths revolutions per minute. This representative puffing apparatus comprises the following elements having approximate dimensions as indicated: a cylindrical drum wall 32 of schedule ten stainless steel pipe for use at atmospheric pressure; a second helical member 55 of ribbon flight conveyor flighting having a 12 inch outside diameter, and a three inch left hand pitch; a one-eighth inch thick tubular wall 38 of stainless steel tubing having a nine inch inside diameter; and, a first helical member of stainless steel conveyor flighting having a nine inch outside diameter, and a three inch right hand pitch. Fins 40 are dimensioned to project three-quarters of an inch radially inwardly from the radially inwardly facing surface of tubular wall 38 in order to agitate mingled product bits and granules of heat transfer material passing through centerless screw conveyor 34. This representative continuous puffing apparatus embodying the present invention, when operated at eight and thirty-five hundredths revolutions per minute, must have a length of about twenty-five inches for each minute of residence time desired within the centerless screw conveyor. Although such a puffing apparatus can be operated over a range of rotational velocity, greatly increased velocity results in decreased agitation by the action of centrifugal force pinning the bits 25 and granules 30 outwardly against wall 38, and slower velocities tend to decrease the uniformity of heat transfer between product bits and the granules of heat transfer material.

FIRST ALTERNATE EMBODIMENT An alternate embodiment continuous puffing apparatus 20a which is suitable for operation at elevated pressure is shown in FIG. 5 to comprise drum assembly 21 as shown in FIGS. 1-3, rotary seals 70, 71, stator 72 having infeed chute 24 secured therethrough, discharge plenum 73, infeed valve 74 sealingly adapted to the bottom of hopper 23, discharge valve 75 sealingly adapted to discharge plenum 73, and pressure regulating means 76 connected between a source of pressurizing media such as nitrogen gas and the interior of drum assembly 21.

Infeed valve 74 and discharge valve 75, collectively designated batching valves, are substantially identical. Referring now to FIGS. 6 and 7 of a preferred embodiment batching valve identified as infeed valve 74 (but which could also have been designated discharge valve 75) is shown to comprise: a rotatable core 80; a stationary seal-ring 81; body 82 having flanges 83, 84; and bearing means 95 for rotationally supporting core 80 so that it can be rotated about axis 96 by applying torque to stub shaft 85 or 86. Core 80 has a truncated conical shape, the radially outwardly facing surface being designated sealing surface 87. A cup-shape cavity 88 is formed in core 80 by radially boring through sealing surface 87 so that the intersection between the wall 89 of cavity 88 and surface 87 is wholly surrounded by sealing surface 87. Sealing ring 81 is configured and sized with respect to body 82 and core 80 so that the radially outwardly facing surface of sealing ring 81 sealingly contacts the contiguous surface of body 82 and the radially inwardly facing surface of sealing ring 81 sealingly contacts sealing surface 87 of core so that a pressure differential can be maintained across the valve while core 80 is rotated to transfer successive cupsful of product bits through the valve.

Seal-ring 81 has diametrically opposed apertures 90, 91 bored through it so that the .cavity 88 cOmmunicates with aperture 90 at one position of core 80 and cavity 88 communicates with aperture 91 at a second position of core 80, and so that cavity 88 is sealed so that it communicates with neither aperture 90 or 91 during a portion of the rotational movement of core 80 to transition it from communicating with aperture 90 to aperture 91 and so forth.

Body 82, of batching valve 74, has a first passageway 93 bored through it with which aperture 90 of seal-ring 81 can be registered so that bits of material can pass downwardly through passageway 93 and aperture 90 into cavity 88. As is obvious from FIGS. 6, 7, the diameter d of passageway 93 and aperture 90 is less than the diameter d, of cavity 88 in order to create an'annular void within cavity 88 due to the angle of repose of product bits in cavity 88 for a purpose which will hereinafter be disclosed. Body 82 has a second passageway 94 bored through flange 84 so that aperture 91 in sealring 81 can be registered therewith at the same time aperture 90 is registered with passageway 93. Means, not indicated in FIG. 6, is provided for locking seal ring 81 with respect to body 82 when apertures 90, 91 are registered with passageways 93, 94, respectively. Thus, when product bits are fed downwardly through passageway 93, discrete portions or cupsful thereof are transferred to second passageway 94 by rotating core 80 with suitable means not shown in the figures. Because of the zones where cavity 88 is sealed from communicating with either aperture 90 or 91, such transference of product bits from passageway 93 to passageway 94 can be accomplished while passageway 94 and whatever is in communication therewith is maintained at a pressurized state. Alternatively, the valve is adaptable for being used in the reverse manner if inverted; that is, infeeding through passageway 94 and discharging through passageway 93 while maintaining passageway 93 and whatever is in communication therewith at a pressurized state.

Discharge plenum 73, FIG. 5, has a funnel shape portion for receiving product bits 25 discharged from centerless screw conveyor 34 and for directing this flow of product bits downwardly to discharge valve 75 for removal from the pressurized puffing apparatus 20a.

It will be understood by those having ordinary skill in the puffing art that such an apparatus as alternate puffing apparatus 200 entails heating product bits to a temperature great enough to cause moisture within the product bits to rapidly flash to steam upon being exposed to ambient atmospheric pressure, the formation of steam being precluded within the apparatusby-maintaining the apparatus ata suitable pressure greater than ambient atmospheric pressure. When operated in this manner, the product bits 25 do not puff within the puffing apparatus; rather, product bits 25 puff upon being discharged from the apparatus through the discharge valve 75.

SECOND ALTERNATE EMBODIMENT Referring now to FIG. 8, a portion of pressurizable puffing apparatus 20b which is substantially identical to puffing apparatus 200, FIG. 5, is shown to further comprise means for removing some granules of heat transfer material from annular screw conveyor through a batching valve 100, and for adding granules of heat transfer material to annular screw conveyor 35 through batching valve 101, FIG. 9, during the operation of the pressurized apparatus. This is accomplished by rotating the cores of batching valves 100, 101 (which are substantially identically configured to but may be smaller that valves 74, at such times and at such frequency as necessary to maintain the granules of heat transfer material within the puffing apparatus in a clean state and to replenish them as necessary. As indicated in FIG. 9, taken along 99 of FIG. 8, batching valves 100, 101 enable establishing a bypass loop for a portion of the granules of heat transfer material so that they can be cleaned by cleaner 103 and returned to the drum assembly 21 and replenished as necessary from a salt reservoir 102.

Of course, provision must be made for passing the granules from stationary elements of the apparatus 2 through the revolving drum wall 32 of the drum assembly 21. Referring to FIGS. 8 and 9, this is accomplished by providing: stationary shroud seals 111, 112 and 113; a plurality of circumferentially spaced apertures 115 through drum wall 32; and, a plurality of circumferentially spaced apertures 116 also through the drum wall 32 of drum assembly 21. Thus, as best seen in FIG. 9, granules can be fed into drum assembly 21 through batching valve 101, chute 118, aperture 119 through shroud 110, and apertures 115, and granules 30 can be removed from the rotating, pressurized drum assembly as best seen in FIG. 8 through apertures 116, aperture 117 through shroud 110, and batching valve 100 by rotating the cores of valves 100, 101 by suitable means at the rate or whenever by-pass flow of granules 30 is de-- sired.

OTHER ALTERNATE EMBODIMENTS Referring now to FIG. 10, it will understood without elaborate discussion, by persons having ordinary skill in the art, that the infeed of product bits 25 into continuous puffing apparatus 20, FIG. 1, described hereinbefore can also be accomplished by replacing hopper 23 and chute 24 with the infeed assembly 120 shown in FIG. 10. Infeed assembly 120 comprises a hopper 121 fitted to a screw-type conveyor 122 having a suitable drive 123. Conveyor 122 comprises worm 124 and barrel 125. Indeed, such an infeed assembly enables varying the rate of metering product bits into a drum assembly of a puffing apparatus and enables varying the point of depositing the bits in centerless screw conveyor 34 by telescoping barrel 125 into space 42. For instance, when an adequate supply of product bits is maintained in hopper 121, varying the rate of rotating worm 124 of screw-type conveyor 122 varies the rate of metering product bits therethrough. Sizing conveyor 122 permits the telescoping of the distal end of barrel 125 into the tubular, axially extending void 42 within the centerless screw conveyor 34 of drum assembly 21, FIGS. 1-3. Means, not indicated in the figure, for effecting such telescoping to vary the distance from the infeed end of the centerless conveyor 34 for depositing product bits from the distal end of conveyor 122 to between the flights of centerless conveyor 34 enables varying the residence time of such product bits within the puffing apparatus without changing the rate of rotating the drum assembly of the puffing apparatus. Such variation of the residence time without other parametric changes is beneficial for optimizing the overall operation of the puffing apparatus because it can be accomplished without affecting the agitation and mingling characteristics 5 of centerless screw conveyor 34.

10 as puffing apparatus 20a, FIG. 5, through the use of a suitable sliding seal intermediate barrel 125 and stator 72 and by using a batching valve 74 between hopper 121 and screw-type conveyor 122.

While several particular embodiments of the present 15' invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention and it is intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

What is claimed is: 1. A continuous puffing apparatus having an internal circulation path for granules of heat transfer medium, said apparatus comprising:

a screw-type first conveyor having an infeed end and a discharge end;

an annular-screw-type second conveyor having an inside diameter at least equal to the outer diameter of said first conveyor;

means for supporting and operating said conveyors in concentric relation so that they have opposite conveying senses, the conveying sense of said first con- 35 veyor being from said infeed end towards said discharge end;

means for introducing product bits into said first conveyor;

means intermediate said infeed end and said discharge end for separating said product bits being conveyed through said first conveyor from said granules of heat transfer medium mingled therewith, said granules being of substantially smaller average size than said product bits, said separating 4 means including means for transferring said granules radially outwardly to a first portion of said second conveyor adjacent thereto for forwarding thereby to another portion of said second conveyor adjacent said infeed end of said first conveyor;

50 means for heating to a predetermined temperature a 55 into said first conveyor near said infeed end from said another portion of said second conveyorso that the heated said granules are mingled with said product bits by the action of said first conveyor causing said product bits to be heated; and

means for discharging said product bits from said apparatus upon being forwarded within said first conveyor to said discharge end thereof.

2. The continuous puffing apparatus of claim 1 wherein:

said first conveyor comprises a tubular wall having a centerless first helical member rigidly secured therein so that the radially outwardly facing edge of said first helical member is contiguous the radially inwardly facing surface of said tubular wall;

said second conveyor comprises a cylindrical drum wall having a centerless second helical member rigidly secured therein so that the radially outwardly facing edge of said second helical member is contiguous the radially inwardly facing surface of said drum wall, said second helical member being of opposite hand relative to said first helical member;

said second conveyor having said first conveyor rigidly secured inside said second helical member so that the conveyors are concentric;

said separating means comprises a foraminous portion of said tubular wall having openings which are sized to freely pass said granules but which openings substantially preclude said product bits from passing therethrough.

3. The continuous puffing apparatus of claim 2 further comprising a plurality of fins secured inside said first conveyor to assist agitation and mixing of said product bits and said granules.

4. The continuous puffing apparatus of claim 2 further comprising means for maintaining the space inside said first conveyor at a pressure different from ambient pressure outside said apparatus.

5. The continuouspuffing apparatus of claim 2 further comprising means for feeding additional granules into said second conveyor and removing some granules from said second conveyor during the operation of said apparatus whereby a portion of said granules can be passed through ancillary equipment external said apparatus for cleaning and ultimate return to said second conveyor, and whereby the quantity of granules within said second conveyor can be replenished as needed.

6. The continuous puffing apparatus of claim 2 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product bits within said first conveyor can be varied.

7. The continuous puffing apparatus of claim 3 further comprising means for maintaining the space inside said first conveyor at a pressure different from ambient pressure outside said apparatus.

8. The continuous puffing apparatus of claim 3 further comprising means for feeding additional granules into said second conveyor and removing some granules from said second conveyor during the operation of said apparatus whereby a portion of said granules can be passed through ancillary equipment external said apparatus for cleaning and ultimate return to said second conveyor, and whereby the quantity of granules within said second conveyor can be replenished as needed.

9. The continuous puffing apparatus of claim 3 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product bits within said first conveyor can be varied.

10. The continuous puffing apparatus of claim 7 further comprising means for feeding additional granules into said second conveyor and removing some granules from said second conveyor during the operation of said apparatus whereby a portion of said granules can be passed through ancillary equipment external said apparatus for cleaning and ultimate return to said second conveyor, and whereby the quantity of granules within said second conveyor can be replenished as needed.

11. The continuous puffing apparatus of claim 7 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product bits within said first conveyor can be varied.

12. The continuous puffing apparatus of claim 10 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product its within said first conveyor can be varied.

13. The continuouspuffing apparatus of claim 1 further comprising means for maintaining the space inside said first conveyor at a pressure different from ambient pressure outside said apparatus.

14. The continuous puffing apparatus of claim 1 further comprising means for feeding additional granules into said second conveyor and removing some granules from said second conveyor during the operation of said apparatus whereby a portion of said granules can be passed through ancillary equipment external said apparatus for cleaning and ultimate return to said second conveyor, and whereby the quantity of granules within said second conveyor can be replenished as needed.

15. The continuous puffing apparatus of claim 1 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product bits within said first conveyor can be varied.

16. The continuous puffing apparatus of claim 13 further comprising means for feeding additional granules into said second conveyor and removing some granules from said second conveyor during the operation of said apparatus whereby a portion of said granules can be passed through ancillary equipment external said apparatus for cleaning and ultimate return to said second conveyor, and whereby the quantity of granules within said second conveyor can be replenished as needed.

17. The continuous puffing apparatus of claim 13 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product bits within said first conveyor can be varied.

18. The continuous puffing apparatus of claim 16 fur- 19. A continuous puffing apparatus for internally circulating a quantity of granules of heat transfer material and for passing a stream of product bits to be puffed through said apparatus, said apparatus comprising:

a. a drum assembly having an input end and a discharge end, said drum assembly comprising two 20 oppositely pitched concentric screw conveyors rigidly secured together, said conveyors being designated an inner screw conveyor and an annular screw conveyor, said drum assembly having a cylindrical drum wall, said drum wall also being the outer wall of said annular screw conveyor, each said conveyor having an input end and a discharge end, said input end of said inner conveyor and said discharge end of said annular conveyor being adjacent each other and disposed at the input end of said drum assembly, said discharged end of said inner conveyor and said input end of said annular conveyor being adjacent each other and disposed at the discharge end of said drum assembly;

b. means for introducing bits of product to be puffed into the input end of said inner conveyor;

0. means for rotating said drum assembly causing granules of heat transfer material and said product bits disposed between the flights of said inner conveyor to be conveyed from the input end of said drum assembly towards said output end whereby the bits of product to be puffed and granules of heat transfer material are mingled;

means for separating said heat transfer material from said product bits within said drum assembly and transferring said heat transfer material to between the flights of said annular conveyor whereby it is conveyed by the action of the flights of said annular conveyor as the drum assembly is rotated to move the heat transfer material towards said discharge end of said annular conveyor;

e. means for heating said heat transfer material as it is conveyed through said annular conveyor;

f. means for transferring said heat transfer material from said discharge end of said annular conveyor into said input end of said inner conveyor; and

g. means for discharging said product bits from said drum upon their reaching said discharge end of said inner conveyor. 

1. A continuous puffing apparatus having an internal circulation path for granules of heat transfer medium, said apparatus comprising: a screw-type first conveyor having an infeed end and a discharge end; an annular-screw-type second conveyor having an inside diameter at least equal to the outer diameter of said first conveyor; means for supporting and operating said conveyors in concentric relation so that they have opposite conveying senses, the conveying sense of said first conveyor being from said infeed end towards said discharge end; means for introducing product bits into said first conveyor; means intermediate said infeed end and said discharge end for separating said product bits being conveyed through said first conveyor from said granules of heat transfer medium mingled therewith, said granules being of substantially smaller average size than said product bits, said separating means including means for transferring said granules radially outwardly to a first portion of said second conveyor adjacent thereto for forwarding thereby to another portion of said second conveyor adjacent said infeed end of said first conveyor; means for heating to a predetermined temperature a stream of said granules while being forwarded from said first portion to said another portion of said second conveyor; means for transferring said granules radially inwardly into said first conveyor near said infeed end from said another portion of said second conveyor so that the heated said granules are mingled with said product bits by the action of said first conveyor causing said product bits to be heated; and means for discharging said product bits from said apparatus upon being forwarded within said first conveyor to said discharge end thereof.
 2. The continuous puffing apparatus of claim 1 wherein: said first conveyor comprises a tubular wall having a centerless first helical member rigidly secured therein so that the radially outwardly facing edge of said first helical member is contiguous the radially inwardly facing surface of said tubular wall; said second conveyor comprises a cylindrical drum wall having a centerless second helical member rigidly secured therein so that the radially outwardly facing edge of said second helical member is contiguous the radially inwardly facing surface of said drum wall, said second helical member bEing of opposite hand relative to said first helical member; said second conveyor having said first conveyor rigidly secured inside said second helical member so that the conveyors are concentric; said separating means comprises a foraminous portion of said tubular wall having openings which are sized to freely pass said granules but which openings substantially preclude said product bits from passing therethrough.
 3. The continuous puffing apparatus of claim 2 further comprising a plurality of fins secured inside said first conveyor to assist agitation and mixing of said product bits and said granules.
 4. The continuous puffing apparatus of claim 2 further comprising means for maintaining the space inside said first conveyor at a pressure different from ambient pressure outside said apparatus.
 5. The continuous puffing apparatus of claim 2 further comprising means for feeding additional granules into said second conveyor and removing some granules from said second conveyor during the operation of said apparatus whereby a portion of said granules can be passed through ancillary equipment external said apparatus for cleaning and ultimate return to said second conveyor, and whereby the quantity of granules within said second conveyor can be replenished as needed.
 6. The continuous puffing apparatus of claim 2 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product bits within said first conveyor can be varied.
 7. The continuous puffing apparatus of claim 3 further comprising means for maintaining the space inside said first conveyor at a pressure different from ambient pressure outside said apparatus.
 8. The continuous puffing apparatus of claim 3 further comprising means for feeding additional granules into said second conveyor and removing some granules from said second conveyor during the operation of said apparatus whereby a portion of said granules can be passed through ancillary equipment external said apparatus for cleaning and ultimate return to said second conveyor, and whereby the quantity of granules within said second conveyor can be replenished as needed.
 9. The continuous puffing apparatus of claim 3 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product bits within said first conveyor can be varied.
 10. The continuous puffing apparatus of claim 7 further comprising means for feeding additional granules into said second conveyor and removing some granules from said second conveyor during the operation of said apparatus whereby a portion of said granules can be passed through ancillary equipment external said apparatus for cleaning and ultimate return to said second conveyor, and whereby the quantity of granules within said second conveyor can be replenished as needed.
 11. The continuous puffing apparatus of claim 7 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product bits within said first conveyor can be varied.
 12. The continuous puffing apparatus of claim 10 further compriSing means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product its within said first conveyor can be varied.
 13. The continuous puffing apparatus of claim 1 further comprising means for maintaining the space inside said first conveyor at a pressure different from ambient pressure outside said apparatus.
 14. The continuous puffing apparatus of claim 1 further comprising means for feeding additional granules into said second conveyor and removing some granules from said second conveyor during the operation of said apparatus whereby a portion of said granules can be passed through ancillary equipment external said apparatus for cleaning and ultimate return to said second conveyor, and whereby the quantity of granules within said second conveyor can be replenished as needed.
 15. The continuous puffing apparatus of claim 1 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product bits within said first conveyor can be varied.
 16. The continuous puffing apparatus of claim 13 further comprising means for feeding additional granules into said second conveyor and removing some granules from said second conveyor during the operation of said apparatus whereby a portion of said granules can be passed through ancillary equipment external said apparatus for cleaning and ultimate return to said second conveyor, and whereby the quantity of granules within said second conveyor can be replenished as needed.
 17. The continuous puffing apparatus of claim 13 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product bits within said first conveyor can be varied.
 18. The continuous puffing apparatus of claim 16 further comprising means for conveying said product bits being introduced into said first conveyor through an axially extending portion of the axially disposed tubular void therewithin, said means including means for varying the axial distance from said infeed end of said first conveyor for depositing said product bits between the turns of said first helical member whereby the residence time of said product bits within said first conveyor can be varied.
 19. A continuous puffing apparatus for internally circulating a quantity of granules of heat transfer material and for passing a stream of product bits to be puffed through said apparatus, said apparatus comprising: a. a drum assembly having an input end and a discharge end, said drum assembly comprising two oppositely pitched concentric screw conveyors rigidly secured together, said conveyors being designated an inner screw conveyor and an annular screw conveyor, said drum assembly having a cylindrical drum wall, said drum wall also being the outer wall of said annular screw conveyor, each said conveyor having an input end and a discharge end, said input end of said inner conveyor and said discharge end of said annular conveyor being adjacent each other and disposed at the input end of said drum assembly, said discharged end of said inner conveyor and said input end of said annular conveyor beinG adjacent each other and disposed at the discharge end of said drum assembly; b. means for introducing bits of product to be puffed into the input end of said inner conveyor; c. means for rotating said drum assembly causing granules of heat transfer material and said product bits disposed between the flights of said inner conveyor to be conveyed from the input end of said drum assembly towards said output end whereby the bits of product to be puffed and granules of heat transfer material are mingled; means for separating said heat transfer material from said product bits within said drum assembly and transferring said heat transfer material to between the flights of said annular conveyor whereby it is conveyed by the action of the flights of said annular conveyor as the drum assembly is rotated to move the heat transfer material towards said discharge end of said annular conveyor; e. means for heating said heat transfer material as it is conveyed through said annular conveyor; f. means for transferring said heat transfer material from said discharge end of said annular conveyor into said input end of said inner conveyor; and g. means for discharging said product bits from said drum upon their reaching said discharge end of said inner conveyor. 